The present invention pertains to methods and apparatus for storing and retrieving information and, more particularly, to methods and apparatus for storing and retrieving information from a multidimensional array.
The use of electronic spreadsheets on personal computers marked the beginning of the "microcomputer revolution." Electronic spreadsheets make it possible for people in the business community to become productive on computers quickly, without having to become programmers. The row and column structure, or table format, of electronic spreadsheets gives users an easily understood means for comparing and contrasting numbers and other information.
The proliferation of electronic spreadsheets has caused several problems, however. Within many business entities, a plurality of spreadsheets are employed by a number of users, often working on related matters. Although the same data may be pertinent to some or all of these spreadsheets, these data are entered into, and updated within, each of the spreadsheets independently of each other. For example, an accountant in the financial department and a market analyst in the sales department are likely to use electronic spreadsheets which rely upon the same basic data. Since these data are entered and updated by each spreadsheet user independently, however, these data may be different and the modeling results produced by the spreadsheets inconsistent.
Present spreadsheet systems also do not allow two users to simultaneously work on the same electronic spreadsheet. Even if the personal computers of the various spreadsheet users are connected through a local area network, each spreadsheet, and the data and calculations which it contains, cannot be worked on or updated by two users at the same time.
Another deficiency of present electronic spreadsheet systems are that they are flat, or two-dimensional. Recently, a three-dimensional spreadsheet, known as LOTUS 1-2-3.RTM. Rel. 3.0, has been introduced. Business data, however, often have more than three dimensions. For example, the budget for a department in a large corporation may be structured with expense items as line items and months as column items. If the same structure were applied to all departments in the corporation, this two-dimensional format would require a third dimension. Months would comprise one axis or dimension, expense items a second axis or dimension and departments a third axis or dimension. If this same structure were applied to each of a number of subsidiaries of the corporation and for the current year and a number of forecasted years, the data would require five dimensions. Using present electronic spreadsheets, data for each dimension after the third dimension would require a new spreadsheet.
As spreadsheets become larger, another problem is presented. A budget for a company that lists, e.g., 25 expense items, for a 12-month period, for each of 10 departments, over 5 years, requires 15,000 cells simply to store the raw data. After the analyst enters these data, he or she must locate the data for use in calculations. Current spreadsheet systems provide no simple means for accomplishing this task because they require that the address of each element of the data be known before it can be retrieved. This problem is further exacerbated in three-dimensional spreadsheets which use cryptic cell references that are even more complex than those used in two-dimensional spreadsheets.
The capabilities of current electronic spreadsheets also are limited because they store both raw data and calculation instructions together. Even though two users may be modeling off the same raw data, therefore, two spreadsheets are required, each having the separate calculation instructions and all the raw data.
In many cases, it is desirable to restrict access to a portion of the data in the spreadsheet to some of the users to which the spreadsheet is accessible, e.g., restricting particular users from viewing or changing certain data. Although some electronic spreadsheets are capable of "locking out" certain users, this all or nothing approach is undesirable when only a small segment of the data requires restriction.
Electronic spreadsheets are particularly useful for budgeting, financial consolidation, financial planning, financial analysis, profit and loss reporting, sales analysis, market research, forecasting and other applications involving tabular data. In such applications, it often is desirable to consolidate figures to present, for example, monthly, quarterly and yearly averages for various line and column items. Although current electronic spreadsheets may provide some formulas for determining some of these values, these spreadsheets are limited in the range, flexibility and dimensional variety of consolidation figures available.